Method of burning sulfur



y 5, 1953 G. N. HOUSTON METHOD OF BURNING SULFUR Filed July e. 1948Patented May 5, 95

UNITED STATES PATENT OFFICE;

MET-HOD J5"I SULFUR.

mesne assignments, to Maithiesoii Chemical Corporation; New York, N'-..11,: a corporation of.

Virginia,

This invention relates to sulfur burners and more particularly tocontinuous sulfur vaporizer and burner systems.

Among the several objects of this invention are the provision of sulfurburner systems for producing gas containing sulfur dioxide and vaporphase sulfur relatively freefrom impurities; the provision of systems ofthe type referred to' which giveincreased yields of sulfur dioxide andvapor phase sulfur; the provision of sulfur burner systems which renderpossible closer controlof effl'uen't gas concentrations, and theprovision or sulfur burner systems of the class described which effect asubstantial increase inoperating efficiency and unit production. Otherobjects-Will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations ofelements, steps and sequence of steps, features of construction andmanipulation,- and arrangements of parts Which will be exemplified inthe structures and methods hereinafter described, and the scope of theapplication" of which will be indicated in' the following claims.

In the accompanying drawing, in. which. one of the various possibleembodiments of the invention is illustrated, the single. figure: is aflow diagram showing the various components of. a sulfur vaporizer andburner system of the pres.- ent inventiom Gomme'r'cial grade: sulfur;suclr as; that ob tained by the Frasch' process, normally containsinorganic and organic impurities. These imrpurities, althoughusuallypresentin' only small percentages, are suflicient to contaminateeffluent gases from sulfur burner systems, often to such a degree astorender these gases undesirable for many purposes. Increasing amountsof impurities in the body of molten sulfur due to the removal ofvaporized sulfur cause greater quantities of the contaminants to becarried in the efiiuent gases; One of the primary uses of sulfur dioxideis in the conversion of sulfur dioxide to sulfur trioxide in the contactprocess for manufacturing sulfuric acid. It is of importance' in thisprocess as well as in many other processes that the gases besubstantially dust andimpurity free. 7

Various methods have been utilized in the past for production of apurified eifluent gas from sulfur burners, including purifying thegaseous reaction products or purifying the sulfur that will later bevaporized and burned. There are numerous difliculties with these methodsand tank T with pit I the apparatusuti'lized to effect them. One expedient frequently used to obtain effluent gases of high purity is toshut down from time to time and manually clean out the apparatus.Another is to draw off periodically and discard the sulfur then in thevaporizer burner. Both procedures are uneconomical because the impuresulfur so withdrawn or cleanedout normally contains or-more' sulfur.However, burning sulfur evenwith such a small proportion of impuritiespresentis impossible Without seriously contaminating the gaseousreaction products and in a relatively short time destroying" theefiiciency of a contact catalyst.

In accordance with the present invention a sulfur burner system has beendevised which effici'entl'y produces efliuent gas of high purity.intermittent manual clean-out operations, hot gas filters and otherpurification arrangements are eliminated, together with the expenseassociated therewith. It has been found that by continuously withdrawinga small portion of the molten sulfur being vaporized and burned,purifixing this portion and then returning this purified portion to thebody of molten sulfur, the percentage of impuritiesin the molten sulfurbody may be conveniently maintained below a level whichwill undulycontaminatethe effluent gas.

Referring now to the drawing, thereis indicated' generally atnumeral-i asulfur melting pit. Solid sulfur may be charged into-this pit-eithercrmtinuouslyor intermittently. Melte'd sulfurfrom' pit I is forced bymeans of a pump 3' through a'pi pe 5 to a constant head feed tank '1. Anover-flowline 9- also connects A feed line- H serves todr'ain molt-ensulfur from the bottom of tank 1, through-a pipe [3 to asulfur vaporizerand burner unit l5 controlled by means of a feed control unit IT. Pipe[3 is formed so as to act asa liquid seal to maintain anabove-atmospheric pressure in the space above the molten sulfur in unitP5 Sulfurvaporizeran'd burner-unit l5 includes aivolatili'zat'ion' zoneis of any conventional heat and sulfur'res'istant material such asbrick; an air duct- 2f having oneextremity, whichmay carry an injectorhead 23; submerged beneath the surface of the body of" molten sulfurcontained in the lower portion of chamber i9; an outlet '25 for gaseousreactionproducts leading to a conventional type combustion chamber (notshown); and, an outlet pipe 21. A pump 29 aids the flow of molten sulfurthrough pipe 21 and a line 3| to a purifier unit such as a filter 33.This filter may be of any conventional type, as, for example, aremovable leaf type such as is manufactured by The Niagara FilterCorporation. The purified molten sulfur output of filter 33 is carriedthrough a line 35 to feed control unit I! and from there is returned tothe body of molten sulfur in chamber IS.

The operation is as follows:

Solid sulfur in any convenient shape or size is fed into tank I eitherintermittently or continuously, manually or mechanically. Tank I ismaintained by any conventional heating arrangement at a temperature highenough to keep the sulfur liquid. The sulfur is transferred from pit Ithrough line 5 to feed tank I by action of pump 3. The level of moltensulfur in tank 1 is maintained substantially constant at a predeterminedlevel by properly positioning the inlet of line 9 in the side of tank 1.The sulfur in tank I is maintained fluid by a suificient supply of heatthereto. The amount of molten sulfur drained from tank 1 to unit I5 iseffectively and simply controlled by control unit H, which may be, forexample, a valve.

The molten sulfur enters unit l5 through pipe I3 at substantially thetop surface of the molten sulfur mass contained therein. Air underpressure is transmitted through duct 2| and dispersed through theforaminous under surface of the injector head 23 into the top portion ofthe sulfur body, thus forming air bubbles which course upwardly throughthe sulfur toward the surface. 7 The gaseous reaction products,including sulfur dioxide and vapor phase sulfur, are conducted out ofunit l5 through outlet 25.

This effluent gas comprising vapor phase sulfur and sulfur dioxide isfed into the customary type of combustion chamber (not shown) whereinthe vapor phase sulfur is subjected to oxidation to convert it to sulfurdioxide.

Pump 29 continuously removes a portion of molten sulfur, preferably fromthe bottom portion of the sulfur mass in unit [5. The sulfur thuswithdrawn is fed into filter 33 where impurities are removed. Purifiedsulfur is then carried through pipe 35 to unit IS, the flow thereofbeing easily and accurately controlled by feed control l7.

Organic as well as inorganic impurities in the molten sulfur body inunit are thus maintained at a level where the gaseous sulfur dioxide andvapor phase sulfur effluent from outlet 25 is substantially free fromcontaminants which would otherwise be present. The eifiuent gas may bethen further oxidized in the customary way to convert vapor phase sulfurto sulfur dioxide. This sulfur dioxide gas is of such purity that a hotgas filter may be dispensed with entirely.

The system of the present invention thus increases the overallefficiency in conversion due to the elimination of periodic shutdowns.Loss of sulfur discarded in the purification step is minimized, a savingin power is obtained due to elimination of the hot gas filter and theelimination of plugging of the filter and catalyst beds due to the solidcontaminants in the gases, and closer control is secured over vaporizingand burning of sulfur as well as over effluent gas concentration.

Although a melting pit such as pit l and a constant head feed tank suchas tank 1 are customarily employed and are accordingly shown, they arenot part of the present invention. Similarly, other sulfur purifyingunits than filter 33 may be utilized.

In view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As many changes could be made in the above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description shall be interpreted asillustrative and not in a limiting sense.

I claim:

1. The method of vaporizing and burning sulfur comprising continuouslyintermixing air with a mass of molten sulfur in a volatilization zone,continuously removing gaseous eflluent therefrom, continuously removinga minor portion of said molten sulfur from the lower part of said moltensulfur mass, continuously purifying said minor portion in a zoneseparated from and out of gaseous communication with said volatilizationzone and returning said purified portion to said molten sulfur mass.

2. The method of vaporizing and burning sulfur comprising bubbling airthrough an upper portion of a mass of molten sulfur in a volatilizationzone, continuously removing the gaseous effluent therefrom, permittingthe impurities in said sulfur mass to settle to a lower portion of thesulfur mass, continuously removing a fraction of the lower molten sulfurportion from said z-one, continuously purifying said fraction byfiltration in a zone separated from and out of gaseous communicationwith said volatilization zone, and continuously returning said purifiedfraction to said upper portion of said molten sulfur mass.

3. The method of vaporizing and burning sulfur comprising continuouslyfeeding molten sulfur into an upper portion of a mass of molten sulfurin a volatilization zone, continuously bubbling air through said upperportion, continuously removing the gaseous effluent therefrom,permitting the impurities in said sulfur mass to settle to a lowerportion of the sulfur mass, continuously removing a fraction of thelower molten sulfur portion from said zone, con tinuously purifying saidfraction by filtration, in a zone separated from and out of gaseouscommunication with said volatilization zone, and continuously returningsaid purified fraction to said upper portion of said molten sulfur mass.

GAINES N. HOUSTON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 1,832,013 Gillett Nov. 1'7, 1931 1,948,345 Garofalo Feb. 20,1934 2,053,211 Villars Sept. 1, 1936 2,165,170 Laury July 4, 19392,253,566 Klepetko Aug. 26, 1941 2,295,605 Ridler Sept. 15, 19422,390,400 Taylor Dec. 4, 1945 2,424,495 Neelley July 22, 1947 2,445,112Grace et al. July 13, 1948 2,516,832 Rosenbloom July 25, 1950 2,595 447Brann May 6, 1952

1. THE METHOD OF VAPORIZING AND BURNING SULFUR COMPRISING CONTINUOUSLYINTERMIXING AIR WITH A MASS OF MOLTEN SULFUR IN A VOLATILIZATION ZONE,CONTINUOUSLY REMOVING GASEOUS EFFLUENT THEREFROM, CONTINUOUSLY REMOVINGA MINOR PORTION OF SAID MOLTEN SULFUR FROM THE LOWER PART OF SAID MOLTENSULFUR MASS, CONTINUOUSLY PURIFYING SAID MINOR PORTION IN A ZONESEPARATED FROM AND OUT OF GASEOUS COMMUNICATION WITH SAID VOLATILIZATIONZONE AND RETURNING SAID PURIFIED PORTION TO SAID MOLTEN SULFUR MASS.